This invention generally relates to the preparation of transition metal cyclopentadienyl carbonyl compounds and more specifically to a one step process for making gasoline engine antiknock compounds such as methylcyclopentadienylmanganese tricarbonyl (MMT).
Cyclopentadienylmanganese tricarbonyls are known antiknock compounds and their preparation and use are described, for example, in U.S. Pat. Nos. 2,818,417, 2,839,552 and 3,127,351 whose teachings are incorporated herein by reference. Two steps are usually required to make such compounds. Either the metal carbonyl is treated with a cyclopentadiene derivative, or a metallocene is prepared from a metal salt and the cyclopentadiene anion and the metallocene is then carbonylated. The starting materials (metallocenes and metal carbonyls) are sometimes expensive to prepare, require high pressure equipment, and/or are available in limited supply. The invention provides an efficient, one-step process for preparing transition metal cyclopentadienyl carbonyls from readily available materials.